View-Model Coroutines multi execute-CodePudding

I call a View-Model method from a fragment. After screen rotation, my View-Model is called again. I need to don't destroy my created View-Model because of its values.
I know it is possible to handle it with Coroutines job.
Can you tell me if We have a better method for doing it?

ViewModel

    private var _counterViewModelLiveData = MutableLiveData(0)
val counterViewModelLiveData
    get() = _counterViewModelLiveData
private var job: Job? = null

fun startVmCounter() {
    job?.cancel()
    job = viewModelScope.launch {
        while (true) {
            delay(TimeUnit.SECONDS.toMillis(1))
            _counterViewModelLiveData.value = _counterViewModelLiveData.value!!   1
        }
    }
}

Fragment

    private fun viewModelSaveState(){
    vm.startVmCounter()
    vm.counterViewModelLiveData.observe(viewLifecycleOwner){
        binding.txtViewmodelSaveStateCounter.text = it.toString()
    }
}

Also, I know about SavedStateHandle, but I don't want to destroy my created ViewModel and fetch data again with SavedStateHandle.

CodePudding user response：

Assuming you are retrieving the ViewModel correctly, it shouldn't be recreated. From the code you posted the issue could be that you call viewModelSaveState again after your Fragment is recreated. You want to call startVmCounter only the first time the Fragment is created. To know if that's the case, you can check if the Bundle you get (for example) in onViewCreated is null. On the other hand, it's correct that you call vm.counterViewModelLiveData.observe every time, because otherwise you won't get updates after recreation.

CodePudding user response：

Just place your code from viewModelSaveState() into onCreateView() or onViewCreated().

So the observation is only started when creating the Fragment and not when the configuration changed.